Updating a gas dynamics model using estimates for California sea lions (Zalophus californianus).

Theoretical models are used to predict how breath-hold diving vertebrates manage O2 , CO2 , and N2 while underwater. One recent gas dynamics model used available lung and tracheal compliance data from various species. As variation in respiratory compliance significantly affects alveolar compression and pulmonary shunt, the current study objective was to evaluate changes in model output when using species-specific parameters from California sea lions (Zalophus californianus). We explored the effects of lung and dead space compliance on the uptake of N2 , O2 , and CO2 in various tissues during a series of hypothetical dives. The updated parameters allowed for increased compliance of the lungs and an increased stiffness in the trachea. When comparing updated model output with a model using previous compliance values, there was a large decrease in N2 uptake but little change in O2 and CO2 levels. Therefore, previous models may overestimate N2 tensions and the risk of gas-related disease, such as decompression sickness (DCS), in marine mammals.